CPOS Seminar: New strategies to investigate and improve organic semiconductors doping
Speaker: Francesca Pallini , PhD Student, Department of Materials Science, University of Milano-Bicocca, Milan, Italy
Abstract: Molecular doping is essential to improve transport properties of organic semiconductors for a variety of applications in optoelectronic devices. If both n-type and p-type doping are necessary for the purpose, n-type doping is especially challenging, due to the air instability of the doped semiconductors and of the required electron rich dopants. Among these, the 1-H benzimidazoline derivative DMBI-H has been widely studied, due to its decent air-stability, easy solution processability and generality of application. The performances of this dopant are however still limited by a low miscibility with the semiconductor matrix, that causes its segregation from the conductive host. Moreover, a comprehensive rationalization of the doping mechanism is still lacking, but is fundamental to improve its efficiency in applications. In this talk, I will present new strategies to deal with DMBI-H mediated doping challenges. In the first part, I will discuss the limits of DMBI-H air stability and I will show that its oxidation impurities can act as nucleating agents for the dopant, mitigating the impact of segregation phenomena and leading to unexpected improvements in transport properties. In the second part of the talk, I will introduce H2 detection techniques as a direct method to study doping processes. I will present the use of Gas-Chromatography (GC) and Residual Gas Analysis as tools to demonstrate and quantify H2 evolution during DMBI-H mediated doping and to investigate the reactive sites involved in the process. I will then show the versatility and the powerfulness of the GC method in the investigation of doping processes mediated by other dopants or happening in different conditions.
